BBS data provide the best long-term and continent-wide information about bird populations, but there have been several issues raised with the survey method including disproportionate representation of habitat. This recent Auk publication analyzed the habitat representation sampled at BBS stops compared to the wider landscape.

Citation:Veech, Joseph A., Michael F. Small and John T. Baccus. Representativeness of land cover composition along routes of the North American Breeding Bird Survey. The Auk. Vol. 129, No. 2 (April 2012), pp. 259-267Abstract:The North American Breeding Bird Survey (BBS) is an annual transect point-count survey of >500 species and >3,500 survey routes (transects). Observers drive and record birds seen and heard within a radius of 400 m of 50 survey points (“stops”�) evenly spaced along a 39.4-km survey route. Thus, the land area along both sides of a route composes a linear or curvilinear landscape. Although BBS data have been used in many studies and conservation plans, there have been few attempts to determine how well the landscapes along BBS routes represent landscapes at larger spatial extents, particularly with regard to land-cover composition. Using data from the 2001 National Land Cover Database, we conducted a study of representativeness of 3,230 routes by comparing the differences in percent cover of 15 land-cover types in BBS landscapes (buffer width of 0.4 km surrounding a route) to larger local landscapes (10 km buffer width) and regions. At the local level, BBS landscapes were representative for most of the cover types except open water, which was underrepresented, and lightly developed open space, which was overrepresented. At the regional level, the collective composition of BBS landscapes was very similar to the composition within entire Bird Conservation Regions. Overall, these results should encourage the continued use of BBS data in ornithological and ecological research and in conservation planning.